The air conditioning device includes a heat exchanger for performing heat exchange between the air in a room and a refrigerant in order to adjust a temperature in the room. There is a known heat exchanger in which a plurality of heat transfer tubes (refrigerant flow passages) is arranged in plural steps in the up and down direction, one end sides of the heat transfer tubes are respectively connected to a refrigerant flow divider via flow division capillaries, while the other end sides of the heat transfer tubes are respectively connected to a header via communication tubes (refer to Patent Literature 1). In a case where this heat exchanger functions as an evaporator, the refrigerant flows from the refrigerant flow divider to the heat transfer tubes via the flow division capillaries, performs the heat exchange with the air while flowing through the heat transfer tubes so as to become a gas refrigerant, and flows and joins into the header via the communication tubes and then is suctioned by a compressor.